Laminated veneer lumber comprising veneer sheets which are obtained by cutting a log into a thickness of 2-3 mm by a rotary lathe or a slicer, and by laminating and bonding the same with the grain directions arranged primarily in parallel is widely used as the material for structures and fixtures of a wooden house such as a door, a door frame, a door casing and a door stop, and for various other items and as a hardwood structural material that combines a decorative material such as a faceplate, a frame and a leg of furniture, a wall trim for ceiling, a skirting, and a base, a faceplate, a door or a counter top of a cupboard.
Laminated veneer lumber (hereinafter LVL) is obtained from logs of broad-leaved trees such as lauans and beech wood, or of acicular trees such as North American woods, Japanese cypress and cedar by chopping the log into cross segments of a given length and cutting the segments into veneer sheets of 2-3 mm thickness using a rotary lathe. Veneer sheets thus obtained are dried using a veneer drier, laminated by arranging them in parallel in the grain direction, and bonded with adhesive. The laminated veneer sheets are subjected to cold press for provisional compression prior to hot press for heat compression. Alternatively, the laminated veneer sheets may be simply subjected to continuous press processing. Subsequently, the lamination of veneer sheets is flattened, cut into a given width and ground on its surface alone with a sander to obtain an LVL.
The prior art method of manufacturing LVL is defective in that a rotary-cut or sliced veneer sheet is generally wavy over its entirety rather than flat. It is difficult to flatten the veneer sheet obtained by the prior art method even if drying is conducted under pressure, and wavy veneer sheets cannot be firmly bonded with one another when laminated using adhesive.
It is also extremely difficult to obtain a laminated veneer lumber which is generally flat even if the lamination of veneer sheets is subjected to cold and hot presses, or simply to a continuous press processing.
It is therefore an object of the present invention to provide an efficient method of mass-producing a laminated veneer lumber of high quality and to provide an excellent decorative sheet by subjecting the laminated veneer lumber thus obtained to a very simple processing.